1. Field of the Invention
The present invention relates to an electric motor and more specifically to a disk drive apparatus provided with the motor.
2. Description of the Related Art
Conventionally, a spindle motor is mounted to a disk drive apparatus such as a hard disk drive. A conventional brushless motor disclosed in Japanese Patent Application Publication No. 2007-295666 includes an attachment plate, a substantially cylindrical bushing, a thrust plate, a sleeve, and a shaft. The bushing is fitted to a fixing hole of the attachment plate. The thrust plate is fixed to the lower portion of the bushing. The sleeve is made of an oil-impregnated sintered material and is press-fitted to the inner circumferential surface of the bushing. The shaft is inserted into the sleeve. The shaft is supported in the radial direction by the sleeve and is supported in the thrust direction by a thrust washer arranged on the upper surface of the thrust plate.
A conventional motor for disk devices disclosed in Japanese Patent Application Publication No. 2003-153481 includes a bracket, a bearing as a ball bearing, a rotor, and a stator. The bracket is fixed to a chassis of a disk device. The bracket includes an inner cylinder portion extending in the axial direction. The bearing is fixed to the inside of the inner cylinder portion. A shaft portion of a rotor is rotatably supported by the bearing. A stator core of a stator is fixed to the outer circumferential surface of the inner cylinder portion. The inner circumferential portion of the stator core contacts the bottom surface portion of the bracket. Coils are formed in the outer circumferential portion of the stator core. The outer circumferential portion of the stator core is positioned axially above the inner circumferential portion thereof. Since the outer circumferential portion of the stator core is separated from the bottom surface portion, it is possible to prevent the coils and the bottom surface portion from interfering with each other.
However, in a motor in which a rotary unit is rotatably supported by a lubricant, it is necessary to suppress vaporization of a lubricant held within a bearing mechanism.